Electrical musical instrument



Feb. 24, 1942. HAMMOND ELECTRICAL MUSICAL INSTRUMENT Filed April '7, 1941 4 Sheets-Sheet l [/2 uenzor Z a are/25'. Hammond Feb. 24, 1942. L, HAMMOND ELECTRICAL MUSICAL INSTRUMENT 4 Sheets-Sheet 2 Filed April '7, 1941 .1 fiver? for 641/"? S 6)? 1942. HAMMOND ELECTRICAL MUSICAL INSTRUMENT Filed April 7, 1941 4 Sheets-Sheet 3 Zaurens/Yamm IZ'Q/ L. HAMMOND 2,274,199

ELECTRICAL MUSICAL INSTRUMENT 4 Sheets-Sheet 4 Fgb. 24, 1942.

Filed April 7, 1941 T 0 Q0 u A T 0.5 an

n u u n m n n m m MM WWW v u m w T n n u n n y VQ 025x36 u m i a NQkWk nwq mw any 8? N gyh NU M, w \k I a N IN Mk MU .\k .m om mw .non @N 3 E a mu 3 m N Patented Feb. 24, 1942 UNITED STATES PATENT OFFICE ELECTRICAL MUSICAL INSTRUMENT Laurens Hammond, Chicago, 111.

Application April 7, 1941, Serial No. 387,113

Claims.

My invention relates generally to electrical musical instruments, and more particularly to instruments of the organ type particularly adapted for the accompaniment oi multi-part harmony singing.

In the singing of four part harmony, such for example, as that rendered by choirs in the singing of hymns, and as would be desirable in the singing of hymns by a congregation, the singer must be very well trained in order to sing his part. In fact it is so difilcult for the individual to sing only his part that it is well known that in congregational singing only a relatively small proportion of the congregation is able to carry any part other than the soprano, or the soprano melody an octave lower than it is scored.

The difiiculty that singers of a congregation encounter in endeavoring to carry a part other than the soprano is likewise encountered by members of the choir, and even members of a quartet, requiring a great deal of practice and rehearsal on their part to acquire the ability to sing parts other than the melody part, usually the soprano.

As a result of this difllculty, congregational singing generally lacks the beauty of the four part harmony intended by the composer. and the individual singers fail to obtain the pleasure and satisfaction which would be theirs if they had the ability to sing the various harmony parts.

The accompaniment provided by an organ does not assist the congregation materially in singing the harmony parts since the over-all efiect of the organ accompaniment on the listener is to bring out the melody rather than the harmonic accompaniment parts.

It has been proposed in the past to overcome these difficulties by using four separate organs, each with an organist playing but a single one of the four harmony parts. With the speakers of the four organs located each adjacent the appropriate section of the choir, the singers of each section would hear their parts much more predominantly than the other parts, and would thus be aided in singing the proper note. Such an arrangement, however, requires four separate consoles and requires a conductor for the four organists. Thus, it is not an arrangement which would be practical for use in the average church. Even in the few circumstances where such arrangement would not be prohibitively costly, it would not be as practical as an arrangement whereby a single organist could play on a single console all four parts, with the tones of each part emanating from sound sources respectively located near the singers singing such parts.

It is thus the primary object of my invention to provide a plurality of musical tone producing devices which may be separated sufliciently apart to enable singers to hear the tones emanating from one device much more predominantly than the tones emanating from the other of such devices, and to provide a single console upon which multi-part harmony may be played, the console being one having electrical circuits under the control of its keys to cause the production of their respective harmony parts by the different tone producing devices.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figure l is a perspective view of the instrument illustrating the manner in which it is to be used;

Figure 2 is a wiring diagram of one form of the instrument;

Figure 3 is a perspective view of a preferred modification of the keyboard; and

Figure 4 is a wiring diagram of a preferred modification of the instrument.

Figure 5 is a wiring diagram of a preferred modification of the instrument.

The general principles of the invention are illustrated in Fig. 1 wherein an organist is shown seated at a console having a keyboard 63, the console including a bass speaker 64 and a tenor speaker 66. These speakers may be permanently secured in the console or may be provided with suitable housings and extension cables, so that the speakers may be removed from the console and placed spaced distances from each other and from the console. A soprano speaker 68 is mounted upon a suitable floor stand 10 which is connected to the console 60 by a suitable shielded conductor 12, while an alto speaker 14 is mounted upon a similar floor stand 16 and connected to the console 60 by a shielded conductor 18.

The speakers 64, 66, 68 and 14 are located sufficiently far apart that singers for the various voices may group themselves about their respective speakers in the manner illustrated. The keyboard arrangement of the console is such that when four part harmony is played upon it, the tones of each part will be produced only by the speaker for such part. Under these circumstances each group of singers will be suiliciently close to the speaker for the part which the group is singing that such group will hear its part predominantly over the tones produced by the speakers from which the other parts emanate.

As a result of this arrangement, the various singers are aided in singing their respective parts so that four part harmony music may be rendered effectively without the necessity of having very highly trained singers, and without requiring frequent rehearsals.

The speakers 64, 66, 6B and H are intended to be representative of any suitable musical tone producing devices capable of being controlled from the console 60. For facilitating installation in a church, the sound producing devices may be distributed throughout the congregation.

There are a number of characteristics of four part harmony music which apparently are peculiar to this type of music, particularly as represented by hymns:

(a) The tonal ranges of the four parts overlap each other. For example middle C (261.626 C. P. S.) may be scored to be sung by the bass, tenor, alto or soprano voice.

(b) The score never requires the alto to sing a note higher than that sung by the soprano, nor does the score ever require the bass to sing a note higher than that to be sung by the tenor. This is shown by the fact that musical notation does not provide any means for indicating a soprano note lower than a concurrent alto note, or a tenor note lower than a concurrent bass note. Similarly, the score never requires the alto to sing a note lower than that to be sung concurrently by the tenor.

(c) In hymns, all parts are usually scored to b sung simultaneously. It is seldom that one part only rests.

(d) The gamut of the combined voices does not exceed three octaves plus two semi-tones (Fl-87.307 C. P. S. to G l-783.99 C. P. 5.), i. e., a total of 38 semi-tones so that a keyboard of thirty-eight keys is sufficient for the rendition of practically all hymns as written.

These characteristics of four part harmony music, particularly hymns, lead one to the deduction that it would be mechanically possible to provide an electrical musical instrument, playable by a single player, with a keyboard switching mechanism so arranged that the tones of each of the four parts would be produced by a sound producing device individual to that part, and the primary objective of the invention thus achieved.

However, apparently insurmountable difficulties are introduced in devising a keyboard switching mechanism for such instrument because of the presence in hymns as scored, of a large number of unison notes, i. e. notes which should be sung by both the alto and soprano, or by both the tenor and the bass, or possibly both the alto and tenor. Because it is within the province of the hymn composer to decide which of three notes scored shall be sung in unison by two of the voices, (and no definite rule for deciding this appears to be followed) it is improbable that any switching mechanism for a standard keyboard could be devised which would always follow the composers precept in this respect.

For example, the notes G2, B2, D3 may be scored in a manner to indicate (a) that the tenor and bass are to sing the note G2, alto B2 and soprano D3, or (b) that the bass is to sing note G2, tenor B2 and both alto and soprano are to sing the note D3, or (c) that the bass is to sing note G2, both tenor and alto to sing B2 and soprano to sing D3. In playing these three notes on a standard keyboard three keys would be depressed, and it appears impossibl that a .y switching mechanism, or means of any nature whatsoever, could be devised which could, merely by depression of the three keys, cause the proper notes to be sounded by the four individual sound producing devices, to follow the composers precept as to which of the foregoing systems a, b or 0 should be followed in sounding these notes from the various sound producing devices.

However, the ditliculties set forth in the two preceding paragraphs are not as serious as might at first appear because, in the first place, the mechanism may be designed to follow the system exemplified by only one of the systems a, b or c, preferably the system b, and secondly no discords or lack of harmony Jilld result even if the sound producing devices for the tenor and alto partsoccasionally produced the tones of adjacent higher parts when it should have produced the tones of the adjacent lower part and vice versa.

The switching system of Fig. 2, while it is somewhat complicated, fulfills the necessary conditions of a two part harmony instrument completely, but as a system for producing four part harmony it has the disadvantage that it may, under some conditions, cause the tenornote to be sounded by the alto sound producing device and vice versa.

In Figure 2, representative keys of a keyboard extending from the note C1 to G4 are shown, the keys being designated by reference characters corresponding to the notes. Four oscillators 84, 86, 88, and of simple construction are shown for generating the bass, tenor, alto and soprano frequencies. The oscillators may be substantially identical in construction except for the values of their component elements, and each has its frequency determined by a tuned mesh in the grid circuit comprising a condenser C5 adapted to be connected in parallel with a greater or lesser portion of a tapped inductance Li. A winding L2 in the cathode circuit of the oscillator is inductively coupled to the inductance L1, and provides a means for feedback of energy to the grid circuit.

The outputs of the oscillators I4, 86, I8 and I are resistance and capacity coupled respectively with amplifier and volume control devices 9|, SI, 98 and I", and the outputs of these amplifiers are supplied to the speakers 84, 66, I4 and I respectively.

Each of the keys A23 to G4 is adapted to operate a single-pole double-throw switch I02, these switches being normally in the upper position illustrated, so as to be connected in series. The arrangement is such that the switch of the highest of a plurality of depressed keys effectively disconnects the switches of the lower keys from the circuit. Each of the switches I02 is adapted upon depression to connect a predetermined number of turns of the inductance LI in parallel with the condenser C5, and thereby determine the frequency of oscillation of the oscillator 90. Because of the series arrangement of the switches I02 it will be clear that the oscillator OI will always be tuned to the frequency represented by the highest of a plurality of depressed keys, provided such key lies within the range A28 to G4.

The switching system for tuning the alto oscillator 88 is slightly more complicated since this oscillator must be tuned to the second highest of two or more keys depressed in the sopranoalto range, but if only one key within this range is depressed, the alto oscillator 88 must be tuned to the frequency of such depressed key. This switching mechanism comprises a single-pole double-throw switch I06 for each of the keys of the combined alto and soprano range G2 to G4, a second single-pole double-throw switch I08 for each of the keys of the alto range from G2 to D4, and a single-pole double-throw switch I I as well as a single-pole single-throw switch II2 for each of the keys of the combined alto-soprano range from G2 to G4. The switches are shown in Fig. 2 in their normal positions in which case all of the switches I08 form a series connection between a terminal A and ground, thus shunting the condenser C5 to render the oscillator 88 ineffective.

The series of switches I08 are adapted to connect the terminal B to one of the taps on the inductance L4, which corresponds to the inductance LI. The series of switches IIO, when no keys are depressed, connect the terminal A to the terminal B, while the series of switches II2 under similar conditions are in parallel with the series of switches H0 and likewise form a closed circuit between the terminals A and B.

It will be noted that the arrangement of the switches I06 and I08 is such that when a key is depressed, the operated switch I06 connects the series of switches I08 of pitch lower than the depressed key to the terminal A, and disconnects said lower switches from the terminal B.

In a somewhat similar manner the operation of but one of the keys will break both the circuits through the series of switches H0 and the series of switches II2, but will establish a connection between the switch II 0 of the depressed key and the series of switches II2 higher than the depressed key. Thus, a circuit will be maintined between the terminals A and B when but one key within the range G2 to G4 is depressed. As a result, the switch I08 of the depressed key will complete a circuit from the terminal A through a portion of the winding L4, and thus tune the oscillator to the frequency represented by the depressed key. When but one key within the overlapping portion of the alto-soprano range is depressed, the alto and soprano oscillators will be tuned to the same frequency, and their speakers 68 and 14 will emit unison tones.

When, however, two keys respectively within the soprano and alto ranges are simultaneously depressed, the circuit through this series of switches I I0 and the circuit through the series of switches II2 will each be broken at two places, and therefore the circuit between the terminals A and B will be broken. (For the sake of brevity the latter circuit will hereinafter be referred to as the A-B" circuit.) The operation of the switch I08 associated with the highest of the two keys depressed will therefore not be effective to connect its associated inductance tap to the terminal A.

ing L4 necessary to tune the oscillator 88 to the frequency of the lower of two simultaneously depressed keys will be connected in parallel with the condenser C5, and the oscillator will operate at the frequency of the lower of the two depressed keys.

If three keys within the range G2 to G4 are simultaneously depressed, the A-B circuits will of course be opened, and the second highest of the depressed keys will result in tuning the oscillator 88 to the frequency represented by such second highest depressed key, and at the same time disconnect the remaining lower switches I08 from the terminal A so that depression of any lower key will not have any eflect upon the tuning of the oscillator 88. The key-operated switch circuits associated with the oscillator 88 effectively tune the oscillator to the frequency of the depressed key if only one key within the alto range G2 to D4 is depressed, and tune the oscillator to the frequency represented by the second highest of two or more depressed keys in the altosoprano range, provided that such second highest of the depressed keys lies in the alto range.

Each of the keys CI to D3 is adapted to operate a switch I I4, these switches being single-pole double-throw switches adapted, when the key is depressed, to make contact with appropriate taps on inductive winding L6 and thereby connect a greater or lesser number of turns thereof in parallel with the tuning condenser C5 of the bass oscillator 84. The operation of the switches I in tuning the oscillator 84 is similar to the operation of the switches I02 in tuning the soprano oscillator 90, except that the switches Ill are so arranged in series that the switch H4 of the lowest key depressed causes the corresponding switches for all of the higher keys to be disconnected from the circuit. Thus, the bass oscillator 84 will always be tuned to the frequency represented by the lowest of a plurality of depressed keys provided such lowest key lies within the range C1 to D3. (In actual practice the bass oscillator will usually be tuned to a frequency one octave lower than that represented by the depressed key.)

Each of the keys CI to FSiI is adapted to operate a single-pole double-throw switch II8, a single-pole single-throw switch II8, a single-pole double-throw switch I20, and a single-pole double-throw switch I22. It will be noted, however, that the switches I22 for the keys CI to AI- are omitted. The switches I22 are adapted, upon depression of their associated keys, to make contact with taps on an inductive winding L8 which serves as the tuning inductance for the tenor oscillator 86. The switches II8 normally connect a terminal C with a terminal D, and the switches I I8, being in series parallel with the switches I I8, likewise normally connect the terminals C and D, the circuits between C and D through the switches H8 and H8 being termed a C-D circuit, similar in function to the AB circuit previously described. As a result of this switching arrangement for the keys CI to F3t, the tenor oscillator will be tuned to the frequency represented by the second lowest of a plurality of keys within the range CI to F3Ii, provided this second lowest note lies in the range from AlII alto oscillator 88 except that it is effective on the second lowest of a plurality of depressed keys, while the alto arrangement is effective on the second highest key. In a similar way, the switching arrangement for the bass oscillator 84 corresponds to the switching arrangement for the soprano oscillator 90 except that it is effective to tune the bass oscillator to the frequency of the lowermost key depressed, while the soprano arrangement is such as to tune the oscillator to the highest of a plurality of depressed keys within its range.

Let us assume that the instrument is utilized in playing four part harmony including the chord B1, G2, D4 and G4. Under these circumstances the bass oscillator 84 will be tuned to the frequency of the note Bl due to the operation of its switch H4 in connecting an appropriate portion of the inductance L in the tuning circuit of the oscillator. Likewise, the key G4 will, by the operation of its switch I02, connect the appropriate portion of the inductance LI in the tuning circuit of the oscillator 80 to tune it to the frequency of the note G4. The key G2 will operate the switches H6, H8, I20 and I22 associated therewith, and because of the arrangement of the series switches I I6 and I I8, the normally closed C-D circuit will be opened. As a result, the switch I22 for the key G2 will connect to the tap on the winding L8 necessary to tune the oscillator 86 to the note G2, this circuit being completed through the switch I22 for the key G2, and through the switch I20 for the key BI. Thus, the tenor oscillator 84 will oscillate at the frequency of the note B1, and the bass oscillator 86 will oscillate at the frequency of the note G2.

In a similar manner the alto oscillator 88 will be made to oscillate at the frequency of the note D4. Despite the fact that the A-B circuit will be open because of the operation of two pairs of switches H0 and H2, the switch I08 for the note D4- will be connected to the terminal A because of the operation of the switch I08 for the key G4. Consequently, each of the four oscillators will be tuned to the frequency of its corresponding note of the chord represented by the keys depressed, and the four parts of the harmony will emanate from their respective speakers 64, 66, 68 and I4.

The switching arrangement of Figure 2 will operate satisfactorily in the playing of most four part harmony selections, but presents some difficulties in the rendition of chords having three notes. The switching system, under these circumstances, will of course tune the soprano oscillator 90 to the frequency represented by the highest key depressed, and the lowermost of the keys depressed will properly tune the bass oscillator 84 to the required frequency, provided that the highest and lowest keys are within the soprano and bass ranges respectively. However, the intermediate of the three keys depressed may produce results not intended by the composer, depending upon the location of this intermediate note in the scale, and depending upon the pitch of the other notes simultaneously depressed. Furthermore, the system is somewhat complicated and expensive since, it will be noted, some of the keys operate as many. as ten switches, most of these being double-throw switches.

In an instrument designed to produce the best musical results, it would probably also be desirable to provide additional switches for keying the amplifiers connected to the oscillators so that the tones would have the proper attack and decay characteristics. Such additional switches would also make certain that the amplifiers would be rendered ineffective during the short intervals that th oscillators are having their frequencies of oscillation changed, thus preventing transmission to the speakers of the transients produced incidental to shifting the frequencies of the oscillators.

In the switching arrangement of Fig. 3, most of the complications of the circuits of Fig. 2 are avoided, and by the operation of a suitable switch the player may readily determine whether the tenor or alto speaker shall sound the intermediate note of a three note chord. It thus provides a way of overcoming at least one of the possible disadvantages of the arrangement of P18. 2.

The arrangement of Fig. 3 employs oscillators 84, 88, 88 and for the bass, tenor, alto and soprano voices respectively. These oscillators may be of the same design as those described with reference to Fig. 2, and are adapted to supply their signals (with suitable exceptions hereinafter to be pointed out) to amplifiers 84, 88, 88 and I00 respectively. The amplifiers are connected to supply signals to the speakers 84, 88, I4 and 68 respectively.

Representative keys CI, AI#, G2, A2#, D3, F3#, D4 and G4 are illustrated as operating switches for tuning the oscillators, it being understood that these keys are representative of a complete keyboard extending, for example, from the note C1 to the note G4. The keys A2# to G4 are adapted to operate single-pole double-throw switches I02 as previously described, to tune the soprano oscillator 80 to the frequency of the highest of a plurality of depressed keys within the soprano range. Similarly, the keys G2 to D4 within the alto range are adapted to operate switches I06, I08 as previously described, and to tune the alto oscillator 88 to the frequency represented by the second highest of a plurality of depressed keys within the combined alto-soprano range, providing that such second highest depressed key falls within the alto range. The keys D4# to G4 are each adapted to operate a switch I08 but do not of course have a switch I08.

Switches II4 operated by the keys CI to D3 in the bass range of the instrument are adapted to tune the bass oscillator 84 to the frequency represented by the lowest depressed key within the bass range.

Switches I20 and I22 for each of the keys AI# to F3# in the tenor range of the instrument are adapted to tune the tenor oscillator 88 to the frequency of the second lowest of a plurality of depressed keys within the combined basstenor range, provided of course that such second lowest depressed key lies within the tenor range. It will be noted also that switches I22 are omitted for the keys CI to AI.

As thus far described, the keying arrangement is substantially identical with that disclosed in Figure 2 except for the omission of the AB and 0-D circuits. Without the addition of other circuits, presently to be described, the depression of a key such as D3 would result in sounding a not of this pitch from the soprano speaker 80 and from the bass speaker 04, but the alto speaker I4 and the tenor speaker 66 would not have a signal supplied thereto. To remedy this possible defect, as well as others which will be mentioned hereinafter, a pair of polarized relays I30 and I3I are provided, these relays being adapted to operate switches I32 and I83 respectively. The

switch I32 is arranged to connect the output of soprano oscillator 90 to the amplifier 33 for the alto speaker when the switch is in its normal closed position as shown. Similarly, the switch I33 is adapted to connect the bass oscillator 64 to the tenor amplifier 66 when the switch is in its normal closed position.

The object of providing the polarized relays I30 and I3I is to cause both the bass and tenor speakers 64 and 66 to sound a unison note when but one key within both the tenor and bass ranges is depressed, and similarly, to cause both the soprano and alto speakers 66 and 14 to sound the same note when but one key within the range of both the soprano and alto ranges is depressed. However, it four keys, of four part harmony chords, are depressed, the relays I30 and I3I should be energized to open the switches I32 and I33, and further, if a three note chord with two keys within the bass-tenor range is played, either the relay I30 or the relay I3I should be energized to open its associated switch so that the intermediate note of the three note chord may be sounded by the alto or tenor speaker, as desired.

The means for accomplishing the foregoing results includes a single-pole single-throw switch I34 operated by each of the keys. Each of the switches I34 has one pole thereof connected by conductor I36 with one terminal of a source of current shown as a battery I38. 01 the switches I34 are connected by resistances RI respectively, with a common conductor I40. The conductor I40 is permanently connected to the other terminal of the battery I33 through a resistor R2.

The windings of the relays I30 and I3I each have one terminal connected to a conductor I42 which is connected to the battery I33 at a point intermediate its end terminals. The other terminal of the winding for the relay I30 is connected to a conductor I44, while the other terminal of the winding for the relay I3I has a conductor I45 connected thereto. A resistor R3 connects the conductors I44 and I45, and a switch I46 is adapted to connect the conductor I40 either to conductor I44 or to conductor I46. The switch I46 may be manually operated by the player, being located on the console for operation either by the player's foot, knee, or by a hand operated tablet.

The values of the constants of the relay energizing circuits and the initial polarization of the relays I30 and I3I are such that the current fiow upon depression of one of the keys, and hence closure of one of the switches I34, is insufllcient to operate either oi the relays I30 or I3I. Likewise, the depression of even two keys, and hence the completion of circuits through two of the resistors RI, is insufficient to operate the relays I30 and I3I.

However, when three keys are simultaneously depressed, the current flow through three parallel resistors RI, and hence through the switch I46 to the relays, will be sufficient to cause the energization of the relay to which the switch I46 is directly connected. With the switch I46 in the position shown in Fig. 3, the current flow upon depression of three keys would be sufilcient' to cause operation of the relay I3I, but due to the interposition of the resistor R3 in the energizing circuit for the relay I30, the latter would not be supplied with sufiicient current to cause it to operate.

However, upon depression of four or more keys, the current flow through the four or more par- The other poles 4 cillators.

allel resistances RI would be sumcient, irrespective of the position oi the switch I46, to cause operation of both relays I33, I3I, thus opening the switches I32 and I33.

As a result of these control circuits for the relays, it will be apparent that the apparatus will operate as follows:

(a) When one key is depressed within the range C1 to A2, the tenor oscillator 86 will not oscillate, since its condenser C6 will be shunted through the circuits of the switches I and I22. The bass oscillator 64 will be tuned to the frequency represented by the depressed key, its output being supplied to the bass amplifier 34 and speaker 64, and through the closed switch I33 to the tenor amplifier 96 and its speaker 63. Thus, the tone corresponding to the depressed key will emanate from both the bass and tenor speakers. Similarly, if but a single key within the range D to G4 is depressed, the soprano oscillator is the only oscillator which will be tuned to the frequency corresponding to the depressed key, but the output of the soprano oscillator will be supplied to both the alto and soprano amplifiers 90 and I00 because of the fact that the amplifier 38 for the alto speaker will be connected to the output 0! the soprano oscillator through the closed switch I32. Likewise, if a single key within the range A23 to D3 is depressed, the soprano and bass oscillators 30 and 84 will be tuned to the frequencies represented by the depressed key and their outputs will be supplied respectively to the soprano-alto and bass-tenor amplifiers and speakers, since the relay switches I32 and I33 will be closed. Under the latter circumstances the alto and tenor oscillators 00 and 06 will be rendered inoperative due to the shunting oi their condensers C5 by their respective switch circuits.

(b) The depression of two keys, depending upon their position in the gamut of the instrument, will cause the sounding oi the lower note by the bass and tenor speakers, and the sounding of a higher note by the alto and soprano speakers. If both keys are above the key D3, the notes will sound respectively from the alto and soprano speakers, or if both are below the note A2t the notes will sound from the bass and tenor speakers respectively.

(0) Upon simultaneous depression of three keys of a chord, as is common in four part harmony music, the soprano oscillator 90 will be tuned to the frequency corresponding to the highest key and the bass oscillator 84 will be tuned to the lowest key. Depending upon the position of the switch I46 either both the alto and soprano amplifiers and speakers will be connected to the soprano oscillator, or both the tenor and bass amplifiers and speakers will be connected to the bass oscillator. By operating the switch I46 the player may determine whether the tone corresponding to the intermediate of the three keys depressed will not be sounded by the alto or by the tenor speaker. Upon depression of certain combinations of three keys it is possible that the alto and soprano amplifiers and speakers will both be connected to receive the outputs of both the alto and soprano oscillators. Similarly, upon depression of other combinations of three keys, both the bass and tenor amplifiers and speakers will be connected to receive signals from both the bass and tenor os- However, such combinations will be rather unusual in four part harmony music, and the results stated will not be particularly disadvantageous since each singer will hear the tone which he is to sing. The only disadvantage will be the singer's possible confusion by hearing an additional note, other than the one he is to sing, from his particular speaker..

(d) When four keys are simultaneously depressed both of the relays I30 and BI will be energized to open their switches I32 and I33 so that each amplifier and speaker will be supplied solely with the signal from its associated oscillator, and the tones of the four parts of the chord being played will be produced correctly by their respective speakers.

From the foregoing detailed analysis of the operation of the circuit of Fig. 3, it will be apparent that this circuit arrangement has advantages over the circuit arrangement of Fig. 2, particularly in the availability to the player of some control over the selection of the speakers which are to sound the unison note when but three keys are simultaneously depressed, and in the greater simplicity of the circuit as a whole. The circuit of Fig. 3, nevertheless, is comparatively complicated and might not be entirely faultless in practical operation because of possible variations in the operation of the relays, changes in the potential of the source I38, and also due to other possible variable factors.

Because of the complexity of any key operated switching system by which four part harmony may be rendered by playing upon the keyboard in a conventional manner, I prefer to utilize a relatively simple switching system which does not have the disadvantages of the arrangements shown in Figs. 2 and 3. but which requires of the player that he play the alto and soprano parts upon keys apparently an octave higher than as scored. While the keyboard and the technique required are thus not entirely conventional, the deviations from the conventional are so slight as to be inconsequential to the player.

The novel form of keyboard is shown in perspective in Fig. 4 comprising fifty-one keys bearing reference characters from I to 5| inclusive. The keyboard appears to be conventional except for a divider I80 which may be in the form of a rigid block between the keys and 21, or may be in the form merely of a suitable marking on either of the keys 25 and 21, or upon both of these keys, or upon the key 26. As a matter of practical construction, such marking of the division of the keyboard is not essential and in practice may be omitted, since, except for a player using the instrument for the first time, such marking would have little or no utility. Each of the keys I to 5| also bears a designation of the pitch of the tone controlled thereby, and it will be noted that the keys I to 26 control production of tones F1 to F3! inclusive, while the keys 21 to 5| control the production of tones G2 to G4 inclusive respectively.

It will be noted that the octave from G2 to F33 is repeated. By virtue of this arrangement the left hand, by depressing selected keys of the left hand group I to 26, may be utilized to play the tenor and bass parts, while the right hand, by playing on the keys 21 to 5!, inclusive, may control the rendition of the soprano and alto parts. In playing four part harmony upon the instrument the player merely depresses keys apparently an octave higher than normal with the fingers of his right hand. In other respects the music is played exactly as scored.

The key operated switching mechanism by which these improved results may be obtained" is shown in Fig. 5 wherein each of the keys 30 to 5! is shown as capable of operating a single-pole double-throw switch I82 which, in a manner similar to that described with reference to Fig. 2, is adapted to determine the frequency of oscillation of the soprano oscillator 90, the highest of a plurality of depressed keys within this range determining the frequency of oscillation.

Each of the keys 21 to 46 is adapted to operate a single-pole double-throw switch I, these switches being connected in series in such manner that the lowest of a plurality of these switches operated will be effective in tuning the alto oscillator 88. Except for the arrangement of the switching mechanism, the soprano and alto oscillators and 88 may be identical with the corresponding oscillators described with reference to Fig. 2, and the same reference characters have therefore been utilized to designate the corresponding parts.

The bass oscillator 88 has a key switching arrangement substantially identical with that shown in Fig. 2, each of the keys I to 2| being adapted to operate a single-pole double-throw switch I86, the switches being connected in series arrangement such that the lowermost of a plurality of depressed keys within the bass range will determine the frequency of oscillation of the bass oscillator 84.

Each of the keys 6 to 26 inclusive is adapted to operate a single-pole double-throw switch I", these switches being connected in series in such manner that the highest of the depressed keys within this range which will determine the frequency of oscillation of the alto oscillator 86.

From a comparison of the switching arrangement of Fig. 5 with those of Figs. 2 and 3, the greater simplicity of the arrangement of Fig. 5 will become readily apparent. The arrangement of Fig. 5 has the pronounced advantage that the musician may play the selection as scored (with the exception of the octave displacement of the right hand), and each of the harmony parts will automatically and without fail be produced by the oscillator and speaker for that part, irrespective of the unison notes. The only possible condition, which is very rare in four part harmony, under which the switching arrangement of Fig. 5 could not be used in following exactly the score as written, would be when one of the parts rests. Under these circumstances the player would merely have to adjust the volume control for the part in which the rest occurs to a zero value in order to render the desired speaker ineffective.

As shown in Fig. 4, a plurality of tablets I60 may be provided adjacent the keyboard, these tablets being adjustable individually to control the volumes of the outputs of the various speakers. In addition, such tablets may be utilized to control to a limited extent the variation of tone qualities of the various speakers by inserting and removing suitable filtering meshes in the amplifier circuits. The amplifiers and speakers are preferably arranged so that each speaker will deliver a tone differing slightly in quality from the tones supplied by the other speakers, thus further aiding the singers in foil wing their particular parts, and improving the over-all quality of the music produced by the instrument.

By virtue of the fact that each oscillator operates throughout but a limited frequency range, the oscillators, as well as their amplifiers and speakers, may be selected and designed for their particular frequency ranges, with consequent imthe four parts will emanate from their respective speakers. The singers grouped about the speakers for their respective parts will thus be cued to sing their parts, with the result that it will be possible for relatively inexperienced singers to follow their respective parts with little, or no rehearsal. Thus, quartets, choirs and even' whole congregations may very easily and correctly sing four part harmony with consequent pleasure" and satisfaction to the singers and lis-' teners.

In accordance with the principles of the invention disclosed and claimed in my co-pending application Serial No. 347,265, filed July 24, 1940, a bass pedal operated by the player of the instrument may be provided to render the bass oscillator eflective, or to. cause this oscillator, or an additional oscillator, to produce a tone one octave lower than the nominal frequency of the lowest depressed key.

Furthermore, the various volume controls or the outputs of .the tour oscillators may be controlled by a common pedal or other control operated by the player, as well as being capable or having their volumes individually controlled by operation of the tablets It ll.

It will be understood that the particular form of oscillators disclosed are merely representative of any suitable oscillatory audio frequency genmodifications and variations by which substantially the results of the invention may be obtained in substantially the same or in a similar manner.

I claim:

1. In an electrical musical instrument of the keyboard type especially adapted for instruction in multi-part harmony singing, a keyboard comprising a plurality of keys arranged in the normal note sequence for more than an octave, a plurality-of separate melody instruments each capable of playing at one time only one note or notes in octave relationship, a separate speaker for each of said instruments, connections for operating said speakers simultaneously at points sumciently remote from one another to aflord localized sound sourcesfor individual groups of singers, a plurality of electric switches operated by each key or said keyboard, said switches being connected for operating a plurality of said melody instruments'in unison and on the same note when only one key is depressed but onseparate harmony notes when a plurality oI-keys are simultaneously depressed within he same octave:

on the said keyboard, whereb a plurality ,of groups of singers may simultaneously but individually be guided in singing their appropriate harmony parts by hearing their part louder than the parts to be sung by the others.

2. An electrically controlled musical instru ment especially adapted for the accompaniment of multi-partharmony singing. comprising a plurality of musical tone producing units in number at least equal to the number of singing parts to be accompanied, said units being capable respectively of producing musical tones extending throughout the ranges of their related singing.

parts, a single console having keys easily playable by one player in the rendition of all of the notes of a multi-part harmony singing score, and

' a plurality of electrical circuits including switches crating systems, or other tone producing devices capable of being electrically controlled by means of key operated switches. The specific forms of the switching arrangements are not claimed herein, the embodiment shown in Figs. 4 and 5 forming the subject matter of co-pending application Serial No. 387,1l4, filed April 7, 1941.

The claims of this application are drawn to the broad principle of providing a separate musical tone producing apparatus for each of a plurality of harmony parts, and physically spaced relatively far apart, but controlled from a common console in such manner that a musician may play multi-part harmony on the console, and each tone. producing apparatus will produce the tones corresponding to its part as played at the console.

It will be apparent to those skilled in the art that numerous modifications and variations in the form of the apparatus may be made without departing from the fundamental principles of the invention. I therefore desire to include within the scope of the following claims, all such operated by the keys of said console to cause the sounding of one of said units of a tonelcorresponding to the highest pitched key of a plurality of said keys'depressed at one time, and to cause the sounding by another of said units of a tone corresponding to one o! the other of such depressed keys.

3. The combination set forth in claim 2 in which said units include sound emitting parts,

and in which the sound emitting parts of the difierent units are separated sufilciently far apart to enable persons in their vicinity to identify the source of tones emanating from one of said units when at least two of said units are producing musical tones at the same time.

4. The combination set forth in claim 2 in which means are provided separately to control the volume of the acoustic output of each of the.

units.

5. The combination set forth in claim 2 in which each of the units produces tones of quality differing from that of the tones of the unit of nearest pitch range.

LAURENS HAMMOND. 

